1. Field of the Invention
The present invention relates to a zinc alkaline cell using zinc alloy powder as an anode active substance, an alkaline electrolytic solution as an electrolytic solution, and manganese dioxide, silver oxide, oxygen, nickel hydroxide, etc. as a cathode active substance and, more particularly, to a zinc alkaline cell in which improved zinc alloy powder is employed as the anode active substance.
2. Description of Related Art
Heretofore, conventional zinc alkaline cells have the problem in common that the zinc anode is corroded by an electrolytic solution during storage. In order to solve the problem as industrial means, hydrogen overvoltage is elevated by using amalgamated zinc powder containing approximately 5% to 10% by weight of mercury, thereby suppressing corrosion to such an extent as causing no practical problem.
Recently, however, as social demand of cells containing less or no mercury has been increased, various research has been made in order to combat with pollution. For instance, as disclosed in Japanese Patent Publication (kokoku) No. 42,114/1989, there has been employed amalgamated zinc alloy powder containing approximately 0.6% by weight of mercury, which is prepared by amalgamating zinc alloy containing lead or aluminum with an indium-mercury alloy.
It is to be noted that, even if mercury has been reduced to the amount as low as approximately 0.6% by weight, mercury is still contained and the problem with environmental pollution cannot be said to be solved. Also, the amalgamated zinc alloy powder as proposed in Japanese Patent Publication (kokoku) No. 42,114/1989 is expected to reduce its mercury rate to a lesser content, however, the problems may still exist that the anode zinc may cause corrosion and that discharge performance as a cell may be impaired, even if zinc alloy powder for such a cell would not be amalgamated. Hence, the problem with environmental pollution by mercury still persists. Further, from the resource point of view, too, it is desired to reproduce zinc and so on from used dry cells, however, the mercury contained in the cells, whatever the amount of mercury is, causes the problem in the step of reproducing the zinc and so on.